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From "Rahul Akolkar" <rahul.akol...@gmail.com>
Subject Re: [SCXML] Automatic forward of external events to <invoke>'d components ?
Date Fri, 13 Jul 2007 21:35:42 GMT
On 7/12/07, Ingmar Kliche <ingmar.kliche@googlemail.com> wrote:
> 2007/7/6, Rahul Akolkar <rahul.akolkar@gmail.com>:
> >
> > It is my interpretation of, quoted from your reference:
> >
> > "Note that the <invoke> element may be used to invoke an external
> > SCXML interpreter to execute a different state machine. In this case,
> > the external state machine acts as a set of substates of the invoking
> > state. The behavior is thus similar to a complex state defined with
> > <state> child elements."
>
>
> Makes sense for sub machines!
>
> One would expect substates to receive all the same events.
>
>
> I had a look at the implementation of invoke again. It apears that external
> events (i.e. triggerEvents()) are used to feed events into both engines.
> parentEvents() uses it to feed external events occuring at the parent into
> the child engine and the child engine uses it to feed *.invoke.done into the
> parents engine.
>
> But I have missed how the child machine may send events during execution to
> its parent. If you also use external events (i.e. a triggerEvent) to send
> events to the parent, how would you avoid that the same event is forwarded
> again into the invoke'd machine?
>
<snip/>

Do we need to avoid it? An event dispatched using <send> (such as your
example below) would also be received similarly by a child state even
if it originated there. The invoke'd machine can ignore it.


> Also I have not found how events are automatically forwarded from the child
> to the parent. Assume I use a <send event="foo" targettype="scxml"/> within
> the child. This would let an external event occur at the child. Now - taking
> the assumption that an invoke'd child machine behaves like a complex state
> within the parent - I would assume that the external event occuring at the
> child is also fed into the parent.
>
<snap/>

Perhaps. The invoke section is greatly underspecified at this moment
(as is acknowledged on the Commons SCXML site), my hope is that the
next WD will bring some more clarity.

-Rahul

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